The Computer Aided Design and Computer Aided Manufacture (CAD/CAM) technologies was firstly introduced into the design and manufacture of oral fixed restoration in the early 1970s by Professor Francois Duret of France, These technologies brought a great technological revolution in the field of dental restoration. Therein, CAD means using computer as the major technological to create and apply various digital and graphic information for article designation: and CAM means an automatically manufacture technology for article machining via a computer-controlled machining equipment, such as CNC (Computer Numerical Control) milling machine. At present, the CAD/CAM systems can successfully manufacture fixed restorations, such as inlay, veneer, crown, fixed bridge and so on. However, patients have to go to the hospital at least 2-3 times to finish the completely therapeutic process. Such frequent and complex subsequent visits put patients to great inconvenience. With the development of computer technology, a new technology, chair-side digital restoration technology (chair-side CAD/CAM), emerges which can treat patients rapidly.
In Chair-side CAD/CAM system, a Computer Aided Design and Computer Aided Manufacture device is placed at the side of dental chair. After tooth preparation and the like, the tooth model of patient can be obtained through digital technology, and then the data can be analyzed by computer, and a dental prosthesis (restoration) can be designed and manufactured immediately. It will take patient around 30 minutes to finish the completely treatment, without complex subsequent visits. With chair-side CAD/CAM technology, the temporary restoration can be prohibited, the manufacture of restoration can be completed in one-step, thus, saving time for patient, and significantly improving the quality of the restoration. Through digital model scanning, restoration designing and manufacturing the dental restoration can achieve better precision and accuracy, and thus improving the treatment success rate. The problems caused by conventional PFM (Porcelain Fused to Metal) denture and removable denture, such as gingiva discoloration and marginal unfitness, can be greatly reduced, and the patient's satisfaction for the treatment can be improved significantly.
The development of the chair-side CAD/CAM also drives the development of the dental material. At present, there are three kinds of dental materials been developed for chair-side CAD/CAM: machinable ceramic, composite and metal. The machinable ceramic includes glass ceramic, glass-infiltrated hybrid ceramic, alumina, zirconia, and the like. The composite material includes resin composite, resin-infiltrated porous ceramic hybrid material, poly(ether-ether-ketone) (PEEK) material, and the like. The metal is dental titanium and the like.
Among the three materials mentioned above, the resin composite material is an ideal candidate for the dental chair-side CAD/CAM owning to its good toughness, machinability, abrasive resistance, X-ray resistance and easily polishing. In addition, the aesthetic effect thereof is similar to natural tooth. However, the strength of CAD/CAM resin composite is too low with the maximum bending strength of around 240 MPa, which can be applied for non-weight bearing restorations, such as the inlay, onlay, veneer, single crown. CAD/CAM resin composite can not be used for bearing dental restorations, such as bridge, molar tooth and the like.